DESIGN OF 0.35-MM PITCH QFP LEAD AND ITS ASSEMBLY TECHNOLOGY

The solder joint reliability of a 0.35-mm lead pitch, 42-mm wide x 42- mm long x 23-mm high, 396 pin, ceramic quad flat package (QFP) was stu died in terms of: 1) finite element analysis simulation; 2) temperatur e cycling tests between -65 degrees C and +125 degrees C. Using the st udy results, physical design of the QFP leads, in terms of thickness, standoff, and Au surface finish were optimized, If the von Mises stres s of a QFP solder joint can be optimized to be no more 16.7 kilogram s quare millimeters, we can guarantee QFP solder joint reliability over requested design life, Also, we developed a thermocompression (T/C) so ldering process for the QFP.